The only difference between the two is that em is proportionate to its nearest parent that has a font-size, whereas rem is always relative to The em value is the same as the rem value displayed above. Large scales (1.333 or greater) may be challenging to implement effectively, but could work well for portfolios, agencies, some marketing sites, or avant-garde works.
A medium scale is versatile and works well for a wide variety of desktop sites, including blogs and Medium scales (1.15–1.333) have a clear hierarchy, and help to organize sections with subheadings. Small scales (less than 1.2) are subtle and good for both mobile and desktop apps, or the mobile version of a responsive site.
